Vacuum-tube repeater circuits



Nam 11, 254- 1,5143% B. W. KENDALL VACUUM TUBE REPEATER CIRCUITS Filed Aug. 14, 1919 //7 van/0x Bum/7 14 Manda Patented Nov. ll, 1%24.

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BURTON W. KENDALL, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, Y., A CORPORATION OF NEW YOK VACUUM-TUBE REPEATER CIRCUITS.

Application filed August 14, 1919. Serial No. 317,509.

To all whom it may concern:

Be it known that I, BURTON KENDALL, a citizen of the United States, residing at New York, inthe county of New York and State of New York, have invented certain new and useful Improvements in Vacuum- Tube Repeater Circuits, of which the following is a full, clear, concise, and exact description.

This invention relates to vacuum tube repeater circuits and more particularly to means for preventing cross talk between vacuum tube repeaters or amplifiers employed in diiierent lines but connected to a common means for supplying space current.

Where a number of repeaters each in a separate line are located near together it is frequently advantageous to connect them in parallel to a single source of space current. In certain cases, as in the binaural system described below, in which repeaters in sepa rate lines are required to operate substantially exactly alike, a common source of current is employed so that any changes in the source will afiect each repeater equally. In all of these cases and particularly in the binaural system, it is important that electric impulses in one line produce no etl'ect in another line, which would interfere with the proper reception of the signals by the listoner.

It is an object of this invention to provide means permitting vacuum tube repeaters in separate lines to be connected to a common source of direct current, but efiectively insulating them from eachother with respect to pulsating or alternating currents.

A further object of the inventionis to provide a path of low impedance to the alternating components of telephone currents in shunt to the source of direct current in a repeater.

' These objects are accomplished by placing a filter comprising series inductance and shunt ca acity in each branch of the circuit supp ying direct current to the tubes.

In the binaural system, which is employed for determining the position of an obiect from which sound waves are emanating, there are sometimes employed two transmission lines leading to detectors in the form of telephone receivers adapted to be listened to simultaneously by an observer, the sendmg ends of the transmission lines being adapted to be selectively connected to pairs of telephone transmitters, the position and angular relation of which are known to the observer. By observing the difference in the time at which a given sound is heard in the two receivers, the approximate direction of the source of sound can be determined, and by obtaining the direction of the source of sound with respect to a difi'erent pair of transmitters, its position both with respect to direction and distance can be approximately determined. The complete appara tus employed in the system is not shown herein, since it is not believed to be necessary to an understanding of this invention. W

In some instances it has been found desirable to place-thermionic amplifiers in the transmission lines so as to render the sound waves of suflicient strength to be audible to the observer. These amplifiers, as well as all other parts ofthe transmission lines, are

carefully selected and adjusted so as to be as nearly alike as possible. that the amplifiers shall operate alike, com mon sources of current are employed for heating the filaments of both tubes and for In order to insure supplying space current therefor. Since incoming impulses cause {similar amplified impulses in the output circuits it is necessary to provide an alternating current path for these impulses and, as above stated, to place means in the connections to the common source of current to prevent the impulses from passing to the other amplifier.

The invention will be more fully understood from the following detailed descri tion and claims taken in connection with t e accompanying drawing in which the view represents schematically a circuit employed in the binaural system and embodying the invention.

Referring to the drawing by reference numerals, the incoming line conductors 11 and 12 of one of the lines are connected to the primary of a transformer 13. The secondary of transformer 13 is included in the input circuit of the vacuum tube 17 having the filamentary cathode 18, the grid or control electrode 19, and the anode 20. A potentiometer 21 is connected across the secondary of transformer 13. Current for heating the cathode 18 is supplied by a suitable source illustrated in the drawin as a battery 22. A resistance 23 is placed in the portion of the heating current circuit which Nil is included inthe input circuit of the tube 17 and serves to maintain the grid 19 negative with respect to the cathode 18. An adjustable resistance 24 serves to control the temperature of the cathode 18.

A source of current shown as a. battery 25 supplies space current between the cathode 18 and anode 20. This current flows through the primary of the output transformer 26, the secondary of which is connected to the outgoing line conductors 27 and 28. The condenser 29 provides a path for alternating currents in the output c1rcuit.

It will be understood that the amplifier above described is adapted to be inserted in one of the lines of a binaural system. Another amplifier as nearly like the first as can be obtained by selecting the apparatus making up the amplifier, is inserted in the other line of the system and is shown in the drawing for convenience with the circuits reversed, with respect to the top and bottom of the sheet. Corresponding parts are designated by the same reference numorals but with prime marks added, and further descriptions of these parts is unnecessary. For the purpose of rendering the operation of the two amplifiers as near alike as possible and independent of fluctuations in the batteries, the same batteries 22 and 25 are used to supply both tubes 17 and 17 with heating current and space current respectively.

For the purpose of preventing impulses from one line from getting across to the other line through'the common battery connections and also to keep out noises from the battery, a filter is provided in each branch comprising choke coils 30 and 30, condensers 29 and 29 and condensers 31 and 31'. The coils 30 and 30 are of high impedance to audible frequencies, While the.

condensers 29, 31, 29' and 31' are of very low impedance to such frequencies. In

' practice, values of 4 microfarads for condensers 29 and 29', 8 microfarads for condensers 31 and 31 and 25 henrys for coils 30 and 30 were found to be satisfactory.

While one. form of the invention has been illustrated it is to be understood that the inventlon is not limited to the specific form shown, but the equivalents thereof may be used within the scope of the following claims.

What is claimed is:

1. In combination, a plurality of thermionlc repeaters in separate lines, separate sources of alternating currents to be repeated by said repeaters respectively, each repeater comprising a vacuum tube having a cathode and an anode, a source of current having parallel circuit connections to said vacuum tubes respectively for supplylng space current between said electrodes,

and means comprising shunt capacity in said parallel circuits to prevent crosstalk between said lines. i

2. In combination, a plurality of thermionic repeaters in separate lines, each repeater comprising a vacuum tube having a cathode and an anode, a source of current having branched circuit connections to said vacuum tubes for supplying space current between said electrodes, and means comprising series inductance and shunt capacity in said branches to prevent crosstalk between said lines.

3. In combination, a plurality of thermionic repeaters in separate lines, separate sources of alternating currents to be repeated by said repeaters respectively, each repeater comprising a vacuum tube having a cathode and an anode, a source of current having parallel circuit connections to said vacuum tubes respectively for supplying space current between said electrodes, and a wave filter in one of said parallel circuits.

4. In combination, a plurality of thermionic repeaters in separate lines, separate sources of alternating currents to be repeated by said repeaters respectively, each repeater comprising a. vacuum tube having a cathode and an anode, a source of current having branched circuit connections to said vacuum tubes for supplying space current between said electrodes, and a wave filter in each of said branches.

5. In combination, a plurality of thermionic repeaters in separate lines, each repeater comprising a vacuum tube having a cathode, an anode, and a control electrode, separate means for supplying potentials to be repeated to said cathodes and control electrodes of the respective repeaters, a source of current having branched circuit connections to said vaccum tubes for supplying space current between said cathodes and said anodes, and a wave filter in each of said branches for preventing crosstalk.

6. In combination, a plurality of thermionic repeaters in separate lines, each repeater comprising a vacuum tube having a cathode and an anode, a source of current having branch circuit connections to said vacuum tubes for supplying space current between said electrodes, a condenser in circuit with the cathode and anode of each tube and adapted to carry the alternating component of the current passing therethrough, a retardation coil in one of the connections from each tube to the source of space current, and condensive reactance in shunt to said source. v

7. In a thermionic repeater, a vacuum tube comprising a cathode and an anode, a source of heating current for said' cathode, a source of space current for said cathode and anode, said sources having a common terminal, and a condenser forming a, path for the alternating component of said space current, said condenser being connected effectively in shunt to said sources. Y

8. In combination, a plurality of repeaters in separate lines, each repeater comprising a vacuum tube having a cathode and an anode, a common source of heating current for said cathodes, a common source of space current for said cathodes and anodes, means between one of said repeaters and said source of space current to prevent cross talk between said repeaters, and a shunt path for alternating currents between said repeater and said means, saidpath comprising a condenser ef fectively in shunt to said sources to prevent short-circuiting the direct current.

9. In combination, a plurality of thermionic repeaters in separate lines, each repeater comprising a vacuum tube having a cathode, an anode and a control electrode, a common source of current for heating each of said cathodes, a common source for supplying the space current between said cathodes and the corresponding anodes, a connection from each'branch of said heating current circuit to the control electrode of the corresponding repeater, and a resistance between the negative end of each cathode and the corresponding one of said connections.

' 10. In combination, a plurality of thermionic repeaters in separate lines, each repeater comprising a vacuum tube having a cathode and an anode and an output transformer conductively connected to the respective anode, a common source of space current for said vacuum tubes, each of said cathodes being connected to the respective transformer by a path comprising a condenser and by a path comprising said common battery, each of said second paths comprising means to prevent theflow of current variations.

In witness whereof, I hereunto subscribe my name this 21st day of July, A. D. 1919.

BURTON W. KENDALL. 

